While growth in ad exchanges makes serving ads across the Internet in real time cheaper and easier, brands have a dilemma: hedge a bet and pay around $.50 cost-per-thousand impressions (CPM) for an ad that could show up on a premium publisher's site or pay around $500 for the same impression with full control over where it is served and the content next to which it is served.

Steve Sullivan, VP of advertising technology at the Interactive Advertising Bureau, says there is little transparency when advertisers buy inventory from a network, as networks don't always inform brands of the content alongside which the ads will appear.

“Companies that the network buys inventories from might be premium sites that don't want the buyer of the inventory to know that they are selling this low cost inventory, so it is a blind network,” says Sullivan.

To purchase cheap ad inventory without harming company reputation (for instance, by keeping baby food ads from running on porn sites), many brands limit the types of sites their ads appear on and use content verification tools to confirm that this is being done.

For instance, a baby food company submits a list of suitable content sites where its ad should run. Its ad networks or exchanges use content verification tools to automatically restrict the brand's exposure from inappropriate content. These tools often quantify site content on a scale of 1 to 1,000, which allow brands to decide the score against which they are comfortable running ads.

“Protecting the reputation of any brand is critical,” says Alex Tait, director of international digital acquisition at American Express. “As online advertising becomes increasingly automated, we need to be secure in the knowledge adverts are reaching appropriate destinations.”

While content controls have been in place for years, current content verification systems give brands more granular control over which sites run their ads with the addition of content safety tools. “Ad verification just passively points out the problem and shows where your ads ran,” says Scott Knoll, CEO of AdSafe. “Ad safety will work in conjunction with an ad server to look at a page before the ad is running and determine if it should run there.”

But it's not always easy. An ad for children's shoes shouldn't be placed alongside content on dealing with a child's death, but automated technology still might not recognize the inappropriateness.

“Digital itself has sold itself as the perfectly accountable medium, but we...need to check that a brand's criteria has been met before ads are served,” says Richard Foan, group executive director of communication and innovation at Audit Bureau of Circulations U.K.